Scholars of the neurolinguistics of bilingualism have debated about the degree to which the first and second languages of bilingual individuals are subserved by shared or separate neural networks, and the extent to which the two languages are active during processing in one. Examining the relations between language treatment and language improvement in the treated and non-treated languages of bilingual individuals with aphasia can help determine the degree of language independence and interdependence in bilinguals. In this proposed study, constrained language treatment will be administered to monolingual and bilingual individuals with chronic aphasia to examine the efficacy of language treatment and treatment transfer from one language to another. The study will allow us to assess which language components demonstrate transfer of treatment benefits from the treated language to the non-treated language, which will, in turn, allow us to determine separate and shared language components of two languages in the bilingual brain. In addition, the study will produce evidence for the efficacy of constrained language treatment in monolingual and bilingual aphasia.